Perinereis aibuhitensis ( Grube, 1878 )

Ibrahim, Nur Fazne, Ibrahim, Yusof Shuaib, Kan, Kotaro & Sato, Masanori, 2024, Nereidid polychaetes (Annelida) inhabiting the inside of decaying fronds of the mangrove palm Nypa fruticans in a tropical estuary in Malaysia, with special reference to the life history of the dominant species, Namalycastis sp., Journal of Natural History 58 (45 - 48), pp. 2043-2074 : 2060-2063

Perinereis aibuhitensis ( Grube, 1878)

( Figures 13–14 )

Nereis (Perinereis) aibuhitensis Grube, 1878: 89–90 , pl. 5; fig. 3 (type locality: Aibuhit, Palaos Islands, Grube 1878: iii; Horst 1924: 168–169, pl. 33, figs 4–6.

Perinereis aibuhitensis : Russel, 1962: 6–7; Wu 1967: 70; Hylleberg et al. 1986: 3–4, fig 2(a–q); Hutchings et al. 1991: 245–247, fig. 2a–e; Arias et al. 2013: 4, fig. 3(c,d,f); Ibrahim et al. 2017: 116–117, figs 1(a), 3(a–h); Villalobos-Guerrero et al. 2021: 6, fig. 3(a–e).

Material examined

Setiu Wetlands , Terengganu, Malaysia: in front of Pulau Che Hing (Sta. 3) (5.681°N, 102.710 ° E), 26 March 2016, coll. N.F. Ibrahim (0.1 m deep, from sediments), 1 specimen ( BW, 3 mm; BL, 120 mm; UMT-Ann 2190); Muara Kuala Setiu (Sta. M) (5.674°N, 102.721°E), 25 June 2015, coll. Y.S. Ibrahim and N.F. Ibrahim (from sediments), 1 ( BW, 4 mm; BL, 150 mm; UMT-Ann 2191), 6 August 2015, coll. M. Sato et al. (from the inside of the decaying Nypa fronds), 2 ( BW, 1.7, 3.0 mm; BL, 55, 110 mm; NSMT-Pol 113581).

Description

Body cylindrical. Largest complete specimen 4 mm in BW, 150 mm in BL, with 145 chaetigers. Live specimen pigmented dark brown. Preserved specimen pale with brown pigmentation in and around prostomium ( Figure 13 (a)).

Prostomium shorter than wide, trapezoidal in shape with faint median furrow ( Figures 13 (a) and 14(a)). Two pairs of eyes, with distinct lenses, arranged trapezoidally, of same size. Short, triangular antennae, approximately one-quarter length of palpophore. Broad, dome-shaped palps with small, globular palpostyles.

Proboscis with a pair of black jaw; each with 3 or 4 distinct teeth at inner margin ( Figures 13 (b) and 14(a)). Ridges of area VI distally separated from each other; areas VI–V– VI ridge pattern π-shaped, sensu Villalobos-Guerrero (2019).

Paragnath numbers and arrangement ( Figures 13 (a,b) and 14(a)): area I: 2–3 conical paragnaths (cones);area II: 10–15 cones on each side;area III:16–27 cones in central patch,with 3–5 cones laterally separated on each side; area IV: 20–23 cones, without bars; area V: 3 cones in triangle;area VI:2 broad-petite bar-shaped paragnaths in transverse row on each side;area VII– VIII: 37–46 cones in two bands; anterior band consisting of single transverse row of around 10 paragnaths on furrows; posterior band consisting of irregular row of more paragnaths.

Four pairs of tentacular cirri with cirrophores distinct. Posterodorsal tentacular cirri longest, extending posteriorly to chaetiger 5–7 ( Figures 13 (a) and 14(a)).

Parapodia of first two chaetigers uniramous, all following parapodia biramous. Notopodia consists of dorsal cirrus, dorsal ligule, median ligule (= notopodial ventral ligule) in biramous parapodia ( Figure 14 (d–f)). Dorsal cirri slender, not beyond dorsal ligule. Dorsal and median ligules triangular with bluntly tapering tip throughout. Dorsal ligules not enlarged in posterior parapodia.

Neuropodia consisting of acicular ligule, postchaetal lobe, ventral ligule and ventral cirrus throughout. Ventral ligules obtuse at tip throughout. Ventral cirri slender, tapering, smaller than ventral ligules throughout ( Figure 14 (d–f)).

Notochaetae all homogomph spinigers with long serrated blades ( Figure 14 (g)). Upper neurochaetae have homogomph spinigers with long serrated blades ( Figure 14 (h)) and heterogomph falcigers with short serrated blades ( Figures 13 (c), 14(j)). Lower neurochaetae consisting of heterogomph spinigers with long serrated blades ( Figure 14 (i)) and heterogomph falcigers with short serrated blades ( Figure 14 (k)). All blades of heterogomph falcigers straight with elongated non-serrated terminal part.

Pygidium brown, with pair of slender anal cirri ( Figure 14 (c)).

Habitat

Found both inside the decaying fronds of Nypa fruticans and in sediments dug around the Nypa trees in the estuary Setiu Wetlands, Terengganu.

Distribution

Taiwan, Thailand, Malaysia, Indonesia, Palau, Australia ( Grube 1878; Horst 1924; Russel 1878; Wu 1967; Hylleberg et al. 1986; Hutchings et al. 1991; Ibrahim et al. 2017; present study).

Remarks

According to Villalobos-Guerrero et al. (2021), the Malaysian specimens collected in this study key out to Perinereis aibuhitensis . Their paragnath numbers are well comparable with those of specimens collected from Palau (the type locality: Grube 1878), Australia ( Hutchings et al. 1991; Arias et al. 2013), Thailand ( Hylleberg et al. 1986) and Taiwan ( Wu 1967) ( Table 3 ).

Figures

Figure 13. Perinereis aibuhitensis. (a) UMT-Ann 2191. Dorsal view of anterior end with everted proboscis. (b, c) NSMT-Pol 113581: (b) ventral view of anterior end with everted proboscis; (c) heterogomph falciger in upper neurochaetae, chaetiger 4. Scale bars: a, b = 1 mm; c = 0.01 mm.

Figure 14. Perinereis aibuhitensis (UMT-Ann 2191). (a) Anterior end with everted proboscis, dorsal view. (b) Middle body, dorsal view. (c) Posterior end, dorsal view. (d–f) Posterior views of parapodia in chaetigers 25 (d), 65 (e), and 104 (f). (g) Homogomph spiniger in notochaetae, chaetiger 25. (h) Homogomph spiniger in upper neurochaetae, chaetiger 65. (i) Heterogomph spiniger in lower neurochaetae, chaetiger 65. (j) Heterogomph falciger in upper neurochaetae, chaetiger 25. (k) Heterogomph falciger in lower neurochaetae, chaetiger 65. Scale bars: a–c = 1 mm; d–f = 0.2 mm; g–i = 0.1 mm; j, k = 0.05 mm.